Bobbin-thread tension threading device for sewing machines



Feb. 18, 1941. Q NISSEN 2,232,624

BOBBIN-THREAD TENSION THREADING DEVICE FOR SEWING MACI-IlNES Filed Oct. 19, 1939 Henry a fvissen Patented Feb. 18, 1941 UNITED STATES PATIENT-@OFFICE BOBBIN-THBEAD TENSION THBEADING DEVICE FOR SEWING MACHINES Henry 0. Nissen, Strattord, Coma, ass! or to The Singer Manufacturing Company, Elfibeth, i N. 1., a corporation of New Jersey Application October 19, 1939, Serial No. 300,098

6 Claims. (01. 112-233) This invention relates to loch-stitch sewing machines and more particularly to lock-stitch sewing machines having a work-supporting arm or horn closely embracing a loop-taker which; func- -tions to cast needle-thre'ad-loops about an unpier-thread mass. o

In a commercially well known class oilockstitch sewing machines, the under-thread mass is wound upon a bobbin removably disposed in acavity of a bobbin-carrierjournaled in the raceway of a loop-taker which is of the horizontalaxis. rotary hook type. The bobbin-carrier is peripherally provided with a tension-spring i'or tensioning the thread leading from the bobbin to the needle-aperture in the work-support. As the bobbin-carrier is directly journaled in the loop-taker, the bobbin alone is removed from the loop-taker when replenishing the under-thread supply and the bobbin-thread therefore hasto be drawn under the thread-carrier tension-spring in the operative position of the thread-carrier in the loop-taker. In flat-bed sewing machines or even in sewing machines having comparatively large work-arms,

there is sufficient space between the loop-taker and the adJacent'wall of the bed-plate or workarm to permit of drawing the bobbin-thread 'under the tension-spring oi the bobbin-carrier. However, when the work-arm which houses the loop-taker is of small compass so as barely to clear said loop-taker, difliculty has been experienced in drawing the bobbin-thread under its tension-spring.

It is an object of the present invention to pro- I vide means for conveniently replenishing the under-thread supply of a sewing machine loop-taker which is contiguous to a frame-wall, of the sewin: machine.

A further object of the invention is to provide means insuring a free bobbin-thread end after replenishment of the bobbin-thread in a lockstitch sewing machine having a work-arm including a removable or openable end-closure member.

Other and more specific objects of the inventhe needle-bar and presser-bar, the work-arm end-closure plate and the bobbin-latch oi. the bobbin-carrier being both open, as when replenishing a bobbin. Fig. 2 is a view in front. elevation of the end portion of the same work-arm. Figs. 3 and 4, respectively. represent perspective views of the bobbin-carrier and'the loop-taker. Fig. 5 is an enlarged front side elevation of the bobbin-carrier. Fig. 6 represents an enlarged section of the bobbin-carrier, substantially on the line 9-6, of Fig. 5. Fig. '7 is an enlarged sectional view of the bobbin-carrier on the line 1-1 of Fig. 6.

The sewing machine in part shown in the drawing has a cylindrical work-arm l upon the free end portion of which is detachably secured, by a screw 2, a correspondingly shaped end-cap 3 provided with a needle-aperture 4. The endcap 3 has an irregular flange 5 partly closing but leaving bobbin-removal clearande at the free III is carried by a rotary loop-taker shaft l3 journaled horizontally in the work-arm I to extend lengthwise thereof. The rim of the looptaker I9 is disposed closely adjacent the endclosure plate I of the end-cap 9, which latter is of small compass and closely embraces the looptaker, whereby endless work of small size may be placed-upon the workarm.

The cup-shaped bobbin-carrier has a peripheral bearing-rib l5 journaled in the raceway I! of the loop-taker, being retained in said raceway by a gib i6 detachablysecured to the looptaker. The bobbin-carrier It also has a flange ll at its rim, said flange being formed with a stop-notch it entered by a stop-finger l9'projectingi inwardly 'fror'n the end-cap flange 5,

whereby the bobbin-carrier is restrained against rotation with the loop-taker. A bobbin 20 is housed by the bobbin-carrier i4 and is rotatable upon the usual bobbin-carrier post 2 upon which latter is pivotally mounted a. bobbin-retaining latch 22. In its closed position, the free end of the latch 22 is disposed in a notch 23 in the bobbin-carrier flange ll.

The front side wall H of the bobbin-carrier I4 is partly cut awayto provide an inverted V- shaped thread-slot 24 open to the flange-notch 23.

Bearing yieldingly upon the-bobbin-carrier side wall l4, adjacent to the rounded apex of the thread-slot 24, is a bobbin-thread tension-spring 2! partly underlying the flange l1 and secured 5 upon the side wall ll of the bobbin-carrier by a screw 22, said spring being adJusted as to tension by'a screw 21. The inwardly bent free end of the tension-spring 2| has a thread-guiding notch 28 overlying a clearance-recess 22 in the bobbinl0 carrier side wall l4.

After a wound bobbin :0 has been inserted in the'bobbin-carrier, upon the post 2i thereof, the end of the bobbin-thread is passed outwardly through the flange-notch 2; and preferably before the latch 22 is closed. To complete the threading of the bobbin-carrier, the bobbinthread is then passed under the tension-spring 25 by drawing the thread upwardly and laterally into the notch 22 in the free end of said spring. While the described loop-taker and bobbincarrier are well known in the art, the employment thereof in a machine having a work-arm of small compass and housing the loop-taker, or having some other analogous frame-structure, renders it difficult to complete the threading of the bobbin-carrier. To obviate this dimculty, the front wallof the work-arm end-cap 2 is partly cut away to provide a curved clearance recess in the outer end of said cap and adjacent to the 30 bobbin-carrier tension-spring 25, the edge of the cut-away end-cap flange 5 preferably merging into the cut-away edge of the end-cap defining the recess 30. Extending upwardly in the front wall of the end-cap 3 from the recess 20 therein and in a direction slightly inclined away from the free end of the work-arm is a thread-guiding and detaining slit 3| terminating at its upper end in advance of the needle-aperture 4. The thread-guiding slit 3| is so disposed with respect to the bobbin-carrier ll that when the bobbin-thread leading outwardly through the bobbin-carrier notch 23 is drawn upwardly in the slit 3|, said thread is at the same time drawn under the tension-spring 25 and into the threadguiding notch 28 of said spring. l

By extending the thread-guiding slit 2i upwardly from the clearance-recess 22, the bobbinthread may be rea ly passed into the lower open end of said slit by merely drawing the thread along the edge of the end-cap flange S, which edge continues'into the clearance-recess 30. The bobbin-thread drawn into the thread-guiding slit 3| is loosely detained thereby until the end of the bobbin-thread is pulled out of said slit by g the drawing up of the first needle-thread loop presented to the loop-taker II by the usual needle 22 carried by the vertically reciprocatory needle-bar 23. Consequently, the bobbin-thread is held away from the open end of the end-cap w 3 and is therefore not pinched by closing the endclosure plate 1 of said end-cap.

The end-closure plate I is provided with a leterally bent wing 1' extending into the clearancerecess 30 as a closure therefor conforming in shape with the curved wall of the end-cap. Preferably sufilcient clearance is provided between the end-closure plate wing 'l' and the edge of the recess 20, in the region of the lower end of the thread-guiding slit ii, to afford access to said wing 1' for springing the end-closure plate I outwardly to release the nub I from the end-cap ing for convenientlythreading the bobbin-carrier 1c M and for insuring against pinching of the bobbin-thread by closing the end-cap plate I have been attained by the present invention without sacrificing any portion of the work-arm surface point by a presser-foot 34 which, in the present case, is provided with a finger-guard 3i. Having thus set forth the nature of the invention, what I claim herein is: 10

l. Ina sewing machine, a reciprocatory threadcarrying needle, a loop-taker complemental to' said needle in the formation of stitches, a bobbin-carrier journaled in said loop-taker about which bobbin-carrier needle-thread loops are 15 cast by said loop-taker, bobbin-thread tensioning means upon said bobbin-carrier, a thread-bobbin removably disposed in said bobbin-carrier, a frame structure disposed contiguous to said loop-taker, and thread-guiding means disposed upon said go frame-structure with respect to said bobbin-carrier for directing thread drawn from said bobbin into position for effective engagement by said tensioning means.

2. In a sewing machine, a reciprocatory threada carrying needle, a loop-taker complemental to said needle in the formation of stitches, a bobbincarrier journaled in said loop-taker, means for restraining said bobbin-carrier against rotation with said loop-taker, bobbin-thread tensioning 30 means upon said bobbin-carrier, a thread-bobbin removably disposed in said bobbin-carrier, and a work-arm housing said loop-taker and provided with a thread-guiding slit, said thread-guiding slit being disposed with respect to, said bobbincarrier for directing thread drawn from said bobbin into position for effective engagement by said tensioning means.

3. In a sewing machine, a reciprocatory threadcarrying needle, a work-arm free at one end thereof, a rotary loop-taker shaft within and extending lengthwise of said work-arm, a looptaker carried by said shaft and embraced by the 'free end portion of said work-arm, a bobbincarrier journaled in said loop-taker and restrained against rotation therewith, a bobbinthread tension spring secured to said bobbincarrier at the front side thereof, a thread-bobbin removably disposed in said bobbin-carrier, and thread-guiding means disposed at the front side of said work-arm and contiguous to said bobbincarrier for directing thread drawn from said bobbin into position for effective engagement by said tension-spring.

4. In a sewing machine, a reciprocatory thread- 55 carrying needle, a work-arm free at one end thereof, a rotary loop-taker shaft within and extending lengthwise of said work-arm, a looptaker carried by said shaft at the free end of said work-arm, a cylindrical end-cap detachably se- 59 cured upon said work-arm and open at the free end of said work-arm, a bobbin-carrier journaled in said loop-taker and restrained against rotation therewith, a bobbin-thread tension-spring secured upon the front side wall of said bobbinas carrier, a thread-bobbin removably disposed in said bobbin-carrier, and an openable end-closure plate for said end-cap, said end-cap having a thread-guiding slit in the front wall thereof contiguous to said bobbin-carrier and extending from '10 the open end of said end-cap in a direction to guide thread drawn from said bobbin into position for effective engagement by said tensionspring.

5. In a sewing machine, a reciprocatory thread- 7 carrying needle, a work-arm having an open free end and provided with a clearance recess extending into the front side wall of the workarm from the-open end thereof, a rotary looptaker embraced by the free end portion of said work-arm, a. bobbin-carrier journaled in said loop-taker and restrained against rotation therewith, -said bobbin-carrier being provided in the front side wall thereof with a thread-slot open at the rim of the bobbin-carrier, a bobbin-thread tension-spring secured upon the bobbin-carrier to overlie said thread-slot and bearing yieldingly against the bobbin-carrier wall above said thread-slot, a thread-bobbin removably disposed in said bobbin-carrier, said work-arm having a thread-guiding slit extending upwardly from said clearance recess in a direction to guide thread drawn from said bobbin under said tension-spring, and an openableend-closure plate upon the free end of said work-arm and provided with a wing extending laterally from said plate into said clearance recess.

6. In a sewing machine, a reciprocatory threadcarrying needle, a work-arm'free at one end and lengthwise disposed substantially normal to the path of needle-reciprocation, a loop-taker complemental to said needle and disposed within the free end portion of said work-arm, a bobbincarrier journaled in said loop-taker and restrained against rotation therewith, a threadbobbin removably disposed in said bobbin-carrier, said work-arm having an open free end and a bobbin-thread receiving slit extending into said open free end, and an openable closure-plate for the open end of said work-arm.

HENRY C. NISSEN. 

